Thin-film transistors (to be referred to as TFTs hereinafter) are used to drive the pixels of, for example, an organic electroluminescent (EL) display unit. There are, for example, top-gate TFTs and bottom-gate TFTs as the TFTs.
The top-gate TFTs include, for example, an oxide semiconductor region called a transparent oxide semiconductor (TOS), a gate electrode formed above the TOS and an interlayer insulating film which covers these. In the TOS, source/drain regions and a channel region are formed so as to be self-aligned with respect to the gate electrode.